This application is based on and incorporates herein by reference Japanese Patent Application No. 2000-93769 filed on Mar. 30, 2000.
1. Field of the Invention
The present invention relates to a geared motor.
2. Description of Related Art
As shown in FIG. 8, a geared motor 81 including a motor main body 82 and a speed reducing arrangement 83 secured to the motor main body 82 has been commonly used, for example, as a motor of a power window system. The motor main body 82 has a yoke housing 84 that receives an armature in a rotatable manner. The speed reducing arrangement 83 has a gear housing 88. The gear housing 88 includes a worm housing segment 85, a wheel housing segment 86 and an air passage accommodating segment 87. The worm housing segment 85 receives a worm shaft that extends out from one end of a rotatable shaft of the armature. The wheel housing segment 86 receives a worm wheel 89 that is meshed with the worm shaft.
The worm wheel 89 is connected to an output plate 91 via a rubber damper 90 received in a recess formed in the worm wheel 89. The output plate 91 is connected to an output shaft 92 that extends through and rotatably supported in a through hole of a shaft receiving portion 86a formed in the wheel housing segment 86. The shaft receiving portion 86a rotatably supports the worm wheel 89. When the worm shaft is rotated by a driving force transmitted from the rotatable shaft of the armature, the output shaft 92 is rotated via the worm wheel 89, the rubber damper 90 and the output plate 91. A vehicle door window glass moves downward or upward in a vertical direction based on rotation of the output shaft 92.
The air passage accommodating segment 87 formed in the gear housing 88 is arranged at a base of the worm housing segment 85. An air passage 93 is formed in the air passage accommodating segment 87. The air passage 93 extends from an outer surface of the air passage accommodating segment 87 to an interior of the yoke housing 84.
The geared motor 81 is assembled by connecting the motor main body 82 to the speed reducing unit 83. More specifically, the geared motor 81 is assembled by connecting the yoke housing 84 to the gear housing 88, for example, with bolts and nuts (not shown).
In the geared motor 81, the yoke housing 84 of the motor main body 82 is typically molded from a metal material, and the gear housing 88 of the speed reducing arrangement 83 is typically molded from a resin material. Thus, during the vertical movement of the window glass with the aid of driving force conducted from the geared motor 81, if a load applied on the window glass is excessively large, a corresponding large force is applied on the worm shaft via the worm wheel 89. This large force flexes the gear housing 88 that has a relatively small strength. That is, although the gear housing 88 has the air passage accommodating segment 87 including the air passage 93, the air passage accommodating segment 87 is only arranged at the base of the gear housing 88. Thus, the air passage accommodating segment 87 does not reinforce the worm housing segment 85 and the wheel housing segment 86. Thus, when the gear housing 88 is flexed, disengagement between the worm wheel 89 and the worm shaft is likely to occur.
The present invention addresses the above disadvantage. Thus, it is an objective of the present invention to provide a geared motor including a gear housing that has an improved strength provided by a simple structure to withstand flexing caused by a larger force generated between a worm wheel and a worm shaft, thereby reducing a possibility of disengagement between the worm wheel and the worm shaft upon application of the larger force therebetween.
It is another objective of the present invention to provide a geared motor having a gear housing that has an improved strength provided by a simple structure including an effective air passage communicating an interior of the geared motor to atmosphere such that the gear housing can withstand flexing caused by a larger force generated between a worm wheel and a worm shaft, thereby reducing a possibility of disengagement between the worm wheel and the worm shaft upon application of the larger force therebetween.
To achieve the objectives of the present invention, there is provided a geared motor including a yoke housing and a gear housing. The yoke housing has an opening and receives a motor unit. The gear housing is made of a resin material. Also, the gear housing covers the opening of the yoke housing. Furthermore, the gear housing includes a worm housing segment and a wheel housing segment. The worm housing segment receives a worm shaft that is connected to the motor unit. The wheel housing segment receives a worm wheel that is meshed with the worm shaft. The worm shaft and the worm wheel cooperate together to transmit a rotational force of the motor unit to an output shaft connected to the worm wheel for outputting the rotational force from the geared motor. The geared motor further includes a reinforcing segment that is integrally formed with the worm housing segment in the gear housing. The reinforcing segment extends in a direction away from the yoke housing along the worm housing segment at least from a base end of the worm housing segment beyond an engaging point where the worm shaft is meshed with the worm wheel. The reinforcing segment includes an air passage that communicates an interior of the yoke housing to atmosphere.